A PMMC type voltmeter, having a full-scale reading of 250 V and an internal resistance of 400 kilo-ohms, is connected with the series resistance of 100 kilo-ohms. Calculate the sensitivity of the voltmeter (in Ohms/Volts)

• A. 2400
• B. 24000
• C. 2000
• D. 20000

Answer: (C)

Voltmeter sensitivity (ohm per volt ratings)
The sensitivity of a voltmeter is given in ohms per volt. It is determined by dividing the sum of the resistance of the meter (Rm) plus the series resistance (Rs), by the full-scale reading in volts. In equation form, sensitivity is expressed as follows:
Sensitivity (S) = (Rm + Rs) ⁄ Vfld
Now as per the given question
 
Rm= 400 KΩ
Rs = 100 KΩ
Vfld= 250 V
S = (400 + 100) ⁄ 250
S = (500 × 103) ⁄ 250
S = 2000 ohm/volt